1. Field of the Invention
The present invention relates generally to batteries or fuel cells which convert thermal energy directly into electrical energy by use of a continuous concentration electrochemical cell. More specifically, the present invention relates to an improved battery based on the generation of an electric current utilizing a sulfuric acid (H.sub.2 SO.sub.4) concentration gradient.
2. Description of the Background Art
U.S. Pat. No. 3,231,426, issued Jan. 25, 1966, discloses a continuous concentration cell in which a voltage is obtained and an electric current is generated between a cathode immersed in concentrated sulfuric acid and an anode immersed in dilute sulfuric acid. The reaction cycle which is set up between the electrodes is: ##STR1##
During operatinn of the cell, the concentrated sulfuric acid solution is diluted by water generated at the cathode, while the dilute sulfuric acid solution becomes more concentrated due to the generation of acid at the anode. The difference in acid concentration between the two solutions must be maintained in order to provide continuous generation of electrical energy. The system disclosed in U.S. Pat. No. 3,231,426 maintains the acid concentration gradient by heating the concentrated acid solution to distill off water generated at the cathode. The water which is continuously distilled from the concentrated acid solution is cycled to the dilute acid solution to continually provide dilution of the acid which is generated at the anode.
The above-described system is well suited for its intended purpose. However, during operation of the cell, large amounts of water must be continually distilled from the concentrated acid solution, recondensed and then cycled to the dilute acid solution. This distillation process is not energy efficient and requires additional equipment to handle the copious amounts of water which must be distilled and circulated during operation of the system. It would be desirable to provide a system and method in which a sulfuric acid gradient system is utilized to generate electric energy without requiring the energy inefficient distillation and circulation of relatively large amounts of water.